BUILD FIX: BTIF_MEDIA_FOCUS_NOT_GRANTED should be complied only for SINK

Since BTIF_MEDIA_FOCUS_NOT_GRANTED is only applicable for focus handling
in A2DP SINK scenario it is only defined and protected by
USE_AUDIO_TRACK.

BUG: 26928143
Change-Id: I414bda160270838c9bc911fef9798a95e1f34ec8
diff --git a/btif/src/btif_media_task.c b/btif/src/btif_media_task.c
index f1531d1..610dc97 100644
--- a/btif/src/btif_media_task.c
+++ b/btif/src/btif_media_task.c
@@ -898,7 +898,9 @@
 
 void btif_a2dp_on_init(void)
 {
+#ifdef USE_AUDIO_TRACK
     btif_media_cb.rx_audio_focus_state = BTIF_MEDIA_FOCUS_NOT_GRANTED;
+#endif // USE_AUDIO_TRACK
 }